Page 580 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

it has been consistently deemed that a clear, coherent, and structured clearing of the search area is the only productive means of performing an underwater search.
For an expanded explanation of public safety diving operations, refer to Teather (1994) and Linton et al. (1986) in the bibliography. There are also excellent training courses available to police and fire departments for training as a PSD in traditional scuba diving techniques.
21.3.3 When to use the diver/when to use the ROV
The ROV or the PSD should only be put into the water when a target is “trapped” by some other means (i.e., a sonar/magnetometer target is identified or a narrow search area is identified). The general search navigation procedure should be to start at a known reference point, finish at a known reference point, and maintain positive navigation throughout the search phase so that all of the search area is positively covered with the search instrument.
For the grid search to cover a defined geographical area, search lines should be spaced to the extent of the range of the equipment (with an approximate 10% overlap of coverage for error margin):
• For sonar equipment—to the effective range of the system used
• For visual equipment—to the effective range of the ROV’s camera or diver’s sight (i.e., clarity
of the water)
• For magnetometer equipment, etc.
With a trained and proficient ROV operator on the dive team’s staff, all of the mundane search/ identification of possible targets should be performed by the ROV up to the final identification of the item. The diver should get wet if the physical capability of the ROV system is insufficient to handle the mass/bulk of the item or if the item is of such a fragile or sensitive nature that an ROV would be inappropriate.
21.3.4 Search theory and electronic search techniques
An ROV can be thought of as a delivery platform for a series of sensors. Since ROVs are inher- ently slow-speed platforms, the full search toolbox should address the needs dictated by the opera- tional requirements. If a very small search area is defined (e.g., a possible drowning victim was seen falling off of a dock in an exact location), an ROV with just a camera may be the only requirement if the water clarity is good. If the water clarity is bad, a scanning sonar may be needed to image the victim acoustically. If a large area is defined (e.g., a drowning victim’s last seen point is unknown, thus the search boundaries cover a very wide area), other sensors decoupled from the ROV would be much more effective in covering the search area.
The basic problem with any search is that until you find the item of interest, your time is spent searching where the item is not located. The objective of searching is to positively eliminate an area of interest as a target area with as high a degree of certainty as possible. The job of a PSD is to clear that area as quickly and efficiently as possible, given the resources available.
Finding items underwater is a chess game from opening moves to end game. The search area is defined and then swept to identify possible targets that will need to be prosecuted or classified.
21.3 Public safety diving 579